This invention is related to multiple-component electrical systems such as those used in the power generation industry and, more particularly, to the field of monitoring conditions of electrical generator systems.
In the power generation industry, monitoring the conditions of components of electrical generator systems is essential for the efficient and nonhazardous functioning of such systems. Effective monitoring encompasses detecting and registering conditions in various components including generators, exciters, collectors and large utility transformers. Conventional techniques for monitoring the temperature of such components use thermocouples or resistance temperature detector devices which convey temperature information with conductors. Such devices and techniques, however, are limited and have significant drawbacks. For example, the devices cannot be routed across components operating at high voltage nor where there is a risk of flash-over or electromotive force (emf) distortion. The ability to measure accurately the temperature of a component is thus further limited because temperature measuring devices cannot be positioned in proximity to critical areas whose temperatures it is desirable to monitor. Therefore, critical areas cannot be well-monitored using these conventional devices and methods.
These limitations on monitoring the condition of power generator systems, moreover, often necessitate monitoring by visual means, which, in turn, may require shutting down a system and imposing costs associated with the downtime of the system while visual inspections are performed. Moreover, because visual monitoring can only be undertaken at intermittent intervals, there is no capability for continuous monitoring of electrical system components. Thus, such conventional techniques and devices suffer deficiencies in terms of both efficiency and efficacy. Conventional techniques are more costly whenever monitoring requires suspending system operations. They also are inevitably less reliable when they can not monitor each component""s temperature accurately or can not measure temperature continuously throughout the system.
Other devices and methods have been tried for certain types of components, but these are also subject to limitations and constraints on efficiency and efficacy. For example, U.S. Pat. No. 4,818,975 by Jenkins titled xe2x80x9cGenerator Stator Core Temperature Monitorxe2x80x9d proposes measuring ambient temperature of the stator core of a generator in terms of hydrogen gas (H2) exiting through the stator core. Temperature of the core can be inferred from either of two effects: (1) the hotter the gas, the more frequent the gas molecules impinge on a temperature-responsive liquid crystal so as to block monitored light; and (2) the hotter the gas, the greater the expansion of a housing-mounted flexible bladder thereby influencing the angle and hence amount of light detected. There are at least two limitations with this type of monitoring, however. First, owing to the relative diffusion of gas molecules, gas is a less efficient heat conductor. Accordingly, the hydrogen gas is a less efficient, less reliable conveyor of temperature information. Second, and more fundamentally, this type of monitoring measures only an aggregate or average temperature of the environment surrounding the stator, not the actual temperature of a specific system component. This can be especially limiting given the need to detect and isolate a temperature variation occurring in individual components. Measuring ambient temperature does not permit separate monitoring and detecting of temperature variations in individual components. Detection, moreover, is also delayed until, for example, an overheating condition in a single component contributes sufficient heat to raise the average or ambient temperature surrounding the stator or other electrical system.
U.S. Pat. No. 4,203,326, by Gottlieb et al. titled xe2x80x9cMethod and Means for Improved Optical Temperature Sensorxe2x80x9d proposes an xe2x80x9coptical conductorxe2x80x9d to measure temperature, but does not address directly the problems of the more conventional type conductor temperature information conveyors. Such devices combine an optical core with cladding, along with a jacket to encase the core and clad material. The core and clad material are formed so as to produce a temperature-influenced difference in refractive indexes that is intended to overcome a common problem with such conductors: temperature responsiveness varies linearly with the length of the conductor. But whatever deficiencies may be corrected with respect to this conductor-length factor, such a device registers only a temperature range and does not address other problems described above. Moreover, there are additional limitations inherent in such devices that limit the efficiency with which temperature detection can be performed. For example, thermal disruption of the fiber conductor by melting in the fiber or surrounding cladding disturbs light conduction. Although using different cladding material can compensate for this risk, doing so can further complicate choosing a proper material composition that will provide the correct refractive indexes difference to accurately monitor for temperature variation. Finally, in addition to their above-described complications in achieving a desired result, such devices also are fundamentally limited in the result that is achieved. Specifically, such devices provide detection of only a range of temperatures, thereby providing less-than-desirable accuracy and problematic delay in monitoring for critical conditions like overheating in an electrical system component.
There is thus a critical need for an apparatus or method that overcomes the problems inherent in conventional and optical conductor type devices for monitoring electrical generator components. Specifically, there is the need for a device or method that more accurately and more efficiently measures the temperatures of the distinct components of a power generator system, as well as the ambient temperature of the system at various locations.
In view of the foregoing background, the present invention advantageously provides an apparatus and method for efficiently and efficaciously monitoring the temperature of one or more regions or components of a multiple-component system, such as a power generator system wherein one confronts such inhibiting factors as high voltage and flash-over risk. The present invention advantageously provides a more accurate capability for monitoring temperature and detecting temperature variation in electrical system components. Moreover, although the apparatus and method are described herein in the context of electrical generator systems, they can have wide applicability in other contexts as will be apparent to one skilled in the art. Such uses include monitoring air conditioning systems and other building service devices whose temperatures need to be monitored effectively and efficiently on a substantially continuous basis. Specifically, as described herein, vital temperature information using the apparatus and method of the present invention is directed efficiently and rapidly to a temperature variation monitor so as to monitor critical temperature variations in a direct, efficient, and reliable manner.
Further advantage is provided in that critical temperature information can be conveyed from within the system to a remote site. This provides capabilities for safe, continuous temperature monitoring using the apparatus and method of the present invention. Notwithstanding this significant advantage, the present invention can be used just as effectively for direct local monitoring of a system component""s temperature.
The present invention, moreover, specifically provides the capability of strategically positioning a plurality of temperature monitoring devices or xe2x80x9ctemperature probesxe2x80x9d within any number of selected critical areas within an electrical generator system. Moreover, the present invention allows these temperature probes to be placed adjacent one or more system components or even to be attached directly to the components. This provides capabilities for monitoring and detecting temperature variations of a plurality of discrete components within the system as opposed to only measuring an average temperature in the form of ambient temperature of the overall system. Again, the present invention permits multiple component monitoring from a remote location external to the electrical generator system as well as direct, on-site temperature monitoring.
The apparatus and method of the present invention provide an effective, efficient temperature probe. The temperature probe preferably comprises a light source, a light sensor, and at least one light window contained within a temperature probe container, and wherein the light window further has an associated pair of light guides. Temperature information is conveyed rapidly and efficiently to the outer surface of the temperature probe container. The container is purposely formed of a heat conducting material, preferably having a thermal conductivity coefficient of 100 or more, so as to rapidly convey temperature information from the surface of the container to the inner surface to which are attached one or more light windows. Alternatively, a thermal conducting member can extend through the container to contact at one portion an outer surface or open-air environment and convey temperature information to another portion within the container that is in contact with the one or more light windows.
Thus, using the present invention, one is able to convey temperature information directly via a thermal conductor linking one or more light windows contained within the container of the temperature probe. As already noted, the temperature probe so described can be adjacent or contact one or more electrical system components whose temperature is to be directly monitored. More specifically, the light source and light sensor can be positioned outside of the electrical generator system while the temperature probes are positioned within the system at any selected critical point at which temperature is to be monitored. The light guide pair associated with each light window preferably each has at least one strand to convey light from the light source to the corresponding light window.
Each light window is responsive to temperature in that each window and perviousness to light is a function of the window""s temperature; that is, the amount of light, if any, that will pass through the window will depend on the window""s temperature. For example, a light window formed from a liquid crystal will be more or less permeable to radiant energy in the form of light depending on the temperature of the window. Indeed, depending on the specific properties of the liquid crystal the window may be completely transparent or completely opaque. Accordingly, the intensity of light passing through a light window will depend on the degree to which the liquid crystal is pervious to radiant energy, which in turn is a function of the specific temperature of the crystal. By measuring the intensity of light, if any, one can measure temperature based on the information received by the temperature probe.
Light intensity is determined by the amount of light captured by the second strand of the light guide pair, which, positioned on the opposing surface of the light window, receives any light conveyed to the window from the light source via the first strand. Captured light is conveyed by the second strand of the light guide pair to a light sensor which measures over a roughly continuous range the intensity of the light received via the second strand. Temperature is thus monitored by measuring the intensity of the light which the light windows of a temperature probe are passing to the light sensor. The greater the number of light windows, the finer is the gradation of temperature ranges which can be discerned.
The temperature probes receive temperature information directly and, virtually instantaneously from a thermal conducting connector in communication with a surface of the component whose temperature is to be monitored and convey that information in the form of light-guide transmitted signals, i.e., light, through the light windows contained within the temperature probe container. A specific advantage of the present invention is the ability of the heat conductor to convey accurate temperature information. The conductor is in direct contact with a surface portion of the select component whose temperature is to be monitored. The temperature so measured is that of the specific component rather than an aggregate or average of the system, as taught by existing conventional and optics-based devices.
Whereas other methods and devices detect variation in ambient temperature by registering increased or more rapid average impingement of gas molecules on the surface of a liquid crystal to raise the temperature of the crystal, the present invention uses a heat conductor having high thermal conductivity. More specifically, recognizing that temperature information is transferred more rapidly through a medium having a fixed structural arrangement, the present invention employs a thermal conducting medium that preferably is a metal or other medium having a sufficiently high coefficient of heat conduction. Thus, the translational (or kinetic), rotational, and vibrational energy is transmitted more rapidly and exchanged more efficiently with a temperature-sensitive liquid crystal device. This, then, increases the speed and accuracy with which temperature information can be conveyed, as noted above. Thus the present invention in contrast to other devices and methods advantageously allows earlier and more accurate detection of temperature variation in electrical system components. It is the temperature of the component itself that is conveyed rather than a proxy in the form of the ambient or system environment temperature. The temperature information conveyed is accordingly more accurate because the heat conductor can preferably be a metal, and moreover, the temperature information is conveyed rapidly as compared to conventional and other optics-based devices.
Yet a further advantage is provided by using the light guides described above, which can enable the routing of the temperature probes across virtually any component without the concerns of high voltage or flash-over that would otherwise arise with conventional devices and methods. In a related vein, the lightweight light guides and light windows corresponding to each temperature probe ensure a lighter assembly as compared to conventional temperature monitoring devices. This provides further advantages where weight is a critical factor such as in aerospace and other non-land based applications.
Moreover there is the ability already noted, to utilize multiple temperature probes for monitoring not merely an ambient temperature proxy or average temperature of a multiple-component system, but also to monitor the temperature of each component. These features, then, help enable the additional advantage of measuring distinct components within, for example, the same electrical generator system. Therefore, because distinct temperature information rather than an aggregate is conveyed for each selected component, the individual components can be simultaneously monitored within the electrical generator system, whereas with conventional devices and methods there is no capability for distinguishing which of several components is contributing what temperature to the overall system temperature. Thus, it is possible to effect simultaneous monitoring of the multiple components within an electrical generator systemxe2x80x94generator, exciters, collectors, transformers, etc.xe2x80x94while having the capability to identify through early detection which of the various components may be overheating or otherwise reaching an unacceptable temperature range.